Voltage Controlled Oscillators (VCO's) are important components in wireless communication systems. FIG. 1 is a block diagram illustrating a conventional differential cascaded VCO with an LC tank. The output of stage 102 is input to stage 104 and the output of stage 104 is input to stage 106. The output of stage 106 is negatively fed forward to the input of stage 102 with the positive output being fed into the negative input and the negative output being fed into the positive input. The cascaded stages produce a filtering effect with somewhat improved phase noise, but the circuit tends to consume a large amount of current.
It would be desirable if an improved cascaded VCO could be developed with low phase noise so that the signal to noise ratio in the output signal can be reduced. Furthermore, it would be desirable if the amplitude could be increased without increasing the current drawn by the device.